An oil filtering device attached to a crankcase or an exterior wall of a crankcase cover generally employs a structure, in which oil is caused to flow into a filter chamber containing a filter element from an inlet, which is formed on the crankcase or the wall of the crankcase cover, and filtered by the filter element, and the filtered oil is supplied to a lubricated part such as a crankshaft through an oil outlet and an outlet passage similarly formed on the crankcase or the crankcase cover. Thus, the oil filtering device is disposed around an end of the crankshaft e.g., refer to Japanese Utility Model Laid-Open No. 61-45286.
However, when the oil filtering device is disposed around the end of the crankshaft, the attachment of accessories (a large gear and a clutch or a rotary member such as ACG) to the crankshaft is limited. Thus, it is difficult to miniaturize the crankcase. As a result, there has been a problem that the size of the internal combustion engine is increased.
The present invention has been devised in consideration of the problem.